How to Figure TDNs for Goats

All goats require energy, protein, vitamins and minerals in their diet. One measure of a feed's energy value is TDN or total digestible nutrients. Energy in the feed is required for physical activity, tissue maintenance, growth, fat deposition, reproduction and lactation. Goats store excess energy as fat. Carbohydrates usually supply energy but protein supplements also provide the nutrient. TDN levels range from zero to 100. Most feeds for goats range from 40 to 90 percent TDN.

Things You'll Need

  • Feed composition table
  • Goat nutrient requirement table
  • Scales
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Instructions

    • 1

      Purchase or obtain forage for the goat's diet. A majority of feed for goats consists of roughage such pasture, hay or browse. Browse may be leaves, buds and twigs from vegetation with woody stems. Consult a feed composition table to find the TDN percentage of the roughage. An extensive table is found in the reference from Colorado State University.

    • 2

      Classify the roughage as low or good quality. Low-quality roughage has a TDN percentage of 40 to 55 percent. Good-quality roughage contains 55 to 70 percent TDN. Low-quality roughage may not meet the goat's energy requirement.

    • 3

      Consult a nutrient requirement table such as the table found in the North Carolina State University reference to find the energy requirements for goats. For example, young, growing and lactating goats require a higher TDN percentage.

    • 4

      Compare the TDN content of the roughage with the goat's nutrient requirement. For example, a lactating meat breed doe producing a large quantity of milk requires a diet with 65-percent TDN content. Alfalfa hay contains approximately 58 percent TDN. If only fed alfalfa hay, the doe would have a diet deficient in energy.

    • 5

      Add grains or concentrate feeds to increase the TDN percentage of the diet. Concentrate feeds contain 70 to 90 percent TDN. For example, corn has 86 percent TDN while the TDN content of oats is about 77 percent.

    • 6

      Consult a nutrient requirement table to find the pounds of TDN required in the goat's daily diet. Multiply the pounds of roughage in the diet by the TDN percent. Multiply the pounds of concentrate feed in the diet by the TDN percent. Add these two numbers and compare the sum with the requirement.

    • 7

      Adjust the amounts of roughage and concentrate feeds if the diet is deficient in energy. For example, a 200-pound doe in late pregnancy requires 5 lb. of dry matter feed per day. The diet should contain 2.68 lb. of TDN. If the doe is fed 4.5 lb. of alfalfa hay and 1/2 lb. of corn, multiply 4.5 lb. by 58 percent (TDN content of alfalfa hay) and .5 lb. by 86 percent (TDN content of corn grain). The sum is 2.75, slightly more TDN than is required by the doe.